Field of the Invention
The present invention relates to an apparatus and a method for detecting an object from an image.
Description of the Related Art
Conventionally, in a digital still camera, a camcorder and the like, a function to detect a human face from an image during imaging is known. Such a face detecting function is highly useful for automatically bringing the human face into focus and adjusting exposure of the human face. Here, the face detecting function is achieved by checking numerous detecting windows extracted from an input image against dictionary data previously obtained by learning using a huge number of face images.
In recent years, two functional expansions are expected for the face detection function of this kind. One is to detect not only the human face but also a pet such as a dog, a cat or the like, and the other is to cut out an area of the face (or another object) detected using the face detecting function from the imaged image.
As for the former functional expansion, a method of, in an image obtained by imaging an object being a detection target, previously registering an image in each detecting window including the relevant object or a feature quantity of the image in a dictionary as object image information, and then detecting the object from an input image by referring to the dictionary is disclosed in, e.g., Japanese Patent Application Laid-Open No. 2011-86261. Besides, as for the latter functional expansion, a method of previously learning a mask representing an object region of a specific object (hereinafter, called mask data) together with image data thereof and automatically cutting out the object area is disclosed in Luca Bertelli, Tianli Yu, Diem Vu, and Burak Gokturk “Kernelized Structural SVM Learning for Supervised Object Segmentation”, Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, 2011 (hereinafter, called the literature 1).
Here, there are various shapes of the detection targets. Consequently, if the method of detecting the detection target by using the conventional rectangular detecting window is used, the percentage of background areas in the detecting window becomes large depending on the shape of the detection target. For this reason, if the method disclosed in Japanese Patent Application Laid-Open No. 2011-86261 is simply applied, there is a case where recognition accuracy deteriorates due to the influence of background images. On the contrary, in the method disclosed in the literature 1, since the mask representing the object region is used, it is necessary to previously learn the specific object by using the image data and the mask data of the relevant object. For this reason, it is impossible to cut out the object area for the object which is designated upon at the time of registration.
The present invention has been completed in consideration of such problems as described above, and an object thereof is to accurately detect the registered object from the input image and cut out the object area thereof.